1. Field of the Invention
The present invention relates generally to quality control inspection and leak detection of product work piece electrically insulated containers having an electrically conductive solution therein in high speed assembly carrier line systems, particularly to controlled carrier means and methods for carrying, conveying, orientating, and spinning the product work piece containers in a desired line of travel for high frequency high voltage spark testing workstation processing.
2. Description of the Related Art
When carrier system work pieces, such as plastic bottles, liquid containers, glass vials, and ampoules, are manufactured, they are tested to ensure that no holes or leaks are formed therein.
In many industries, it is important to test the fluid tightness and seal integrity of containers. For example, in the food industry, it is essential to ensure that containers in which food products are packed are completely sealed to ensure that the contents are a good condition, free from molds, bacteria and other pathogenic organisms, so they will be safe when used by consumers. The pharmaceutical industry similarly requires that containers for medicines, especially solutions intended for injection or intravenous administration, be protected from contamination or serious danger to public health may result.
Thus, the detection of pinholes, hairline cracks, and defective seals in assembly line product containers is important to the quality control of the product, especially in production environment of varying temperatures. For example, at higher temperatures the solution or product may expand and leak from a pinhole, a crack or defective seal of a container, and at lower temperatures the product can shrink back into the container bringing within such contaminants as bacteria from the exterior of the container.
In the past several approaches have been employed to ascertain the fluid tightness and seal security of containers apart from visual inspection. For example, some test devices use a positive pressure approach wherein an active force on the container is created so as to enable the detection of a substantial movement of a wall of the container which movement is monitored and translated into a leak detection function. Exemplary of such devices are U.S. Pat. Nos. 4,663,964 and 4,771,630 and 5,226,316.
Other testing approaches include optical scanning techniques for inspecting containers for variations that affect optical characteristics of the container. Exemplary of such devices are U.S. Pat. Nos. 4,378,493,4,584,469, 5,200,801 and 5,719,679. In U.S. Pat. No. 5,719,679 to Shimizu et al. there is disclosed a method and apparatus for inspecting a medicine vial with cameras in the course of conveying the vial by a rotary table, comprising the steps of inspecting the vial's lower half at a station of the vial's lower portion while the vial is rotated from above with its head being chucked, inspecting the vials upper half at a station of the vial's upper portion while the vial is supported and rotated from below by a rotary belt adapted to be brought into contact with the vial, and combining these inspections of lower and upper halves to inspect the whole vial from its head to its bottom.
While the foregoing inspection and detection systems have met with limited success, such systems require complex machinery or multiple workstation processing that are time-consuming and inefficient, especially when the system requires a high-speed detection of several hundred containers per minute. Further such systems, particularly those employing vacuum or pressure decay tests, may be destructive causing the loss of good product and packaging components.
An alternative to the foregoing is a system that employs a high frequency high voltage spark test method of inspection. In high voltage leak detection systems, the conductive solution in the container is used as an electric circuit pathway such that small pinholes or hairline cracks or capillary pores which would normally be dosed by the product will be more consistently and effectively detected while reducing the possibility of false rejections. Such systems rely upon the increase in the current volume through the product to determine whether the container is defective (namely, leakage current will be greater than charging current when the container workpiece has a leak and when there is no leak, the container functions as an insulator and the charging current will be greater than the leakage current). Exemplary of such a system is U.S. Pat. No. 6,009,744, the entire disclosure of which is hereby incorporated by reference herein. Further, a high frequency high voltage spark test method of inspection is preferable because it can detect even the smallest pinhole, hair crack, capillary pore or insufficient container wall thickness when the high voltage electrical currents “wash” the container. Pinholes as small as 0.5 microns in diameter can be consistently detected.
However, high frequency high voltage spark test methods of container inspection must rely upon the electrical conductivity of the container solution to obtain electric current circuit readings by an inspection electrode and a cooperative detection electrode that are exposed to the container in a manner avoiding any air pocket or air bubble of the container's interior. Thus, reliable testing of containers in high-speed carrier assembly lines has required multiple arrays of inspection electrodes being exposed to varying multiple positions of the container. For example, a vertically orientated container may have an air pocket in container's upper interior bordering the container's neck and cap in which case the inspection electrode and cooperative detection electrode cannot be exposed adjacent the air pocket. For complete reliable testing of such a container, a first high voltage leak detection test would be directed to the containers lower portion and a second high voltage leak detection test using a repositioned container and a repositioned set of the inspection and detection electrodes would be undertaken to inspect the container's upper portion at a point in time when the air pocket has shifted leaving the electrically conductive solution to close any pinhole, hair crack, capillary pore or deficient wall thickness in the upper portion.
In addition to air pockets within a container, many high voltage spark test leak detection systems are not readily adapted to accommodate rapid, repetitive assembly line processing of carrier borne products or work pieces presented to multiple machine or station operations which require differing specific orientations of the product or work pieces at selected points of the overall assembly line processing procedure.
In U.S. Pat. No. 6,293,387 to Forster there is disclosed a carrier, a carrier orientation and conveying structure, a carrier line system assembly, and a carrier process for orientating and conveying containers to be transported along a desired pathway wherein the pathway has a guide element cooperative with the carrier selected from one of more of the group consisting of a rail for engagement into a transverse slot of the carrier, a rod for engagement into a transverse bore of the carrier, and a boundary barrier to contain the carriers. When the guide element of the pathway includes a cam rail surface upon the rod, selected controlled rotational movement of the carrier circumferentially upon the rod perpendicular to its ongoing lineal path along at least a portion of the length of the rod is achieved. The entirety of U.S. Pat. No. 6,293,387 to Forster is hereby incorporated by reference herein for its disclosure of a carrier, a carrier orientation and conveying structure, a carrier line system assembly, and a carrier process for orientating and conveying containers to be transported along a desired pathway.